1. Field of the Invention
The present invention relates to a method of manufacturing a toner, the toner, a developer, a developing device, and an image forming apparatus.
2. Description of the Related Art
Conventionally, a surface modification treatment for coating the surface of powder particles with a coating material has been performed in order to improve characteristics of the powder particles such as toner particles.
As a method for the surface modification treatment of the powder particles such as toner particles, a method is known that a mechanical stirring force is applied to the powder particles by a rotary stirring section such as a screw, a blade, or a rotor to fluidize the powder particles in a powder flowing passage and a coating material is ejected from a spray nozzle to the powder particles in a fluid state. For example, Japanese Examined Patent Publication JP-B2 5-10971 (1993) discloses a surface modification method of solid particles in which a rotary stirring section is rotated at peripheral speed of 5 to 160 m/sec to fluidize powder particles and a liquid is sprayed from a spray nozzle to the powder particles in a fluid state to adhere fine solid particles contained in the liquid to surface of the powder particles or to form a film of a coating material contained in the liquid on the surface of the power particles. According to the surface modification method disclosed in JP-B2 5-10971, adhesiveness between the coating material and the powder particles is able to be improved and time required for the surface modification treatment is able to be shortened.
Further, Japanese Unexamined Patent Publication JP-A 4-211269 (1992) discloses a method for manufacturing a microcapsule in which resin particles are adhered to the surface of inner core particles and are treated with a solvent that dissolves the resin particles to form a coating layer on the surface of the inner core particles. The method for manufacturing a microcapsule disclosed in JP-A 4-211269 comprises at least a step of adhering the resin particles to the surface of the inner core particles, a step of treating resin particles with a solvent that dissolves the resin particles, and a step of drying and collecting the treated particles.
However, the method disclosed in JP-B2 5-10971 causes the following problem. When the mechanical stirring force is applied by the rotary stirring section to fluidize the powder particles and the liquid containing the coating material is ejected from the spray nozzle to the powder particles in a fluid state, the powder particles need to be isolated and fluidized in order to obtain coated particles in which the powder particles are uniformly coated with the coating material. In order to isolate and fluidize the powder particles, the peripheral speed of the rotary stirring section needs to be increased to a certain extent. When a concentration of the coating material in the liquid to be sprayed is low, an amount of the liquid to be sprayed needs to be increased in order to uniformly coat the powder particles with the coating material. This causes that the powder particles are easily adhered to an inner wall of an apparatus and there is a possibility that other powder particles and coating material aggregate and grow with the adhered powder particles as a core. When the powder particles and the coating material aggregate and grow in the inner wall of the apparatus, there occur problems that a powder passage for fluidizing the powder particles is narrowed and the powder particles are prevented from being isolated and fluidized and that the yield of the coated particles is lowered. Moreover, in the case of not selecting the liquid containing the coating material, there is a possibility that the liquid is retained in the apparatus and the powder particles absorb the liquid to generate an aggregate, thus generating adhesion of the aggregate to the inner wall of the apparatus. Further, there is a possibility that air bubbles are generated in the film of the fine resin particles when the liquid is dried, and the method disclosed in the JP-B 5-10971 (1993) is not directly applicable to resin inner core particles such as a toner.
Since the treatment is performed by using the solvent that dissolves a resin of the resin particles in the method disclosed in the JP-A 4-211269 (1992), the solvent taken in the resin of the resin particles hardly vaporizes and a large amount of the aggregates are generated even when the inner core particles and the resin particles are fluidized at high speed. Further, large amounts are adhered to the inner wall of the apparatus, which are difficult to be collected in a state of primary particles, and the method does not provide excellent productivity. There is a possibility that some kinds of solvents dissolve even the inner core particles so that waxes contained in the inner core particles and the like are adhered and exposed to the surface of the inner core particles as particles, and when using the obtained microcapsule particles as a toner, toner performance including storing performance and fixing performance of the toner is deteriorated.